C++ Area and Circumference of a Circle

#include <iostream>
#include <cmath>

const double PI = 3.14159265358979323846;

double calculateArea(double radius) {
    return PI * pow(radius, 2);
}

double calculateCircumference(double radius) {
    return 2  PI  radius;
}

int main() {
    double radius;

    std::cout << "Enter the radius of the circle: ";
    std::cin >> radius;

    double area = calculateArea(radius);
    double circumference = calculateCircumference(radius);

    std::cout << "Area of the circle: " << area << std::endl;
    std::cout << "Circumference of the circle: " << circumference << std::endl;

    return 0;
}